The Influence of Magnetron Sputtering Conditions on the Structure of Zr–Pd Coatings

Technical Physics Letters - Using the method of DC magnetron sputtering, nonstructured amorphous metal coatings of Zr75Pd25 composition were obtained with an average deposition rate of 1.3 nm/s at...     

The result of a wall failure in-pile experiment under the EAGLE project

The WF (wall failure) test of the EAGLE program, in which 2 kg of uranium dioxide fuel-pins were melted by nuclear heating, was successfully conducted in the IGR (Impulse Graphite Reactor) of NNC/Kazakhstan. In this test, a 3 mm-thick stainless steel (SS) wall structure was placed between fuel pins and a 10 mm-thick sodium-filled channel (sodium gap). During the transient, fuel pins were heated, which led to the formation of a fuel-steel mixture pool. Under the transient nuclear heating condition, the SS wall was strongly heated by the molten pool, leading to wall failure. The time needed for fuel penetration into the sodium-filled gap was very short (less than 1 s after the pool formation). The result suggests that molten core materials formed in hypothetical LMFBR core disruptive accidents have a certain potential to destroy SS-wall boundaries early in the accident phase, thereby providing fuel escape paths from the core region. The early establishment of such fuel escape paths is regarded as a favorable characteristic in eliminating the possibility of severe re-criticality events. A preliminary interpretation on the WF test results is presented in this paper.     

Isolation of lactic whey proteins in the form of complexes with apple pectin

The possibility of isolating lactic whey proteins (LWP) in the form of insoluble complexes (IC) with apple pectin was studied. The effect of pH, ionic strength (mu, NaCl), temperature (T degree C), pectin weight fraction (X3%) and the total concentration of macromolecular components in the system (Ws) on isolation has been considered. The process has been characterized by LWP yield in the composition IC--P, percentage and the extent of protein concentration in the concentrated phase (IC)--F. The mixing of lactic whey with a pectin solution usually yielded an IC (10% less than or equal to X3 less than or equal to 90%). The dependence of P on X3 is of an extreme nature with a maximum of 85% at X3 = 60%. The following conditions correspond to the maximum LWP yield (90%) in the complex composition: pH 3.4, mu = 0.01, T = 5-20 degrees C, X3 = 60%, Ws = 0.5%. At compositions of the system corresponding to the maximum P value (X3 = 60%) practically all the LWP fractions are present in the concentrated phase. If X3 much greater than 60% or X3 much less than 60% alpha-lactalbumin is practically absent in the concentrated phase. Usually, minimum F values (2.5-4.0) correspond to maximum protein yield at X3 = 60%. At X3 greater than 70% and X3 less than 50% F values may be considerably higher (20 times and more). A decrease in the pectin methylation degree from 56.7% down to 15.4% does not affect F. The maximum protein yield (94%) occurs when low methylated pectin is used. The character of the dependence of F on X3 is explained according to similar processes of complex gel formation and the processes of gel formation in polymer solutions.     

Various Scale Levels of the Gel-to-Glass Transformation

The gel-to-glass transition in SiO₂ xerogels prepared by inorganic sol-gel synthesis was studied. The evolution of the molecular structure is traced using the infrared and lowfrequency Raman spectroscopy methods. The elastic moduli of the samples as well as the pore wall moduli at various stages of heat treatment are determined from the data on Brillouin scattering. The formation of monolithic glass on the macroscopic level manifests itself within a narrow temperature range by the dramatic increase of Young's modulus to the accepted value for fused silica. This phenomenon coincides with structural transformations on the molecular scale: (i) the definite correlation radius (the long-range order sphere) appears; (ii) local distortions of the silica network relax. The presence of structural defects influences the kinetics of vitreous SiO₂ formation during xerogel heat treatment.     

Separation of mixtures and distribution of a liquid on a structured packing in a large-scale model of a distillation column

A large-scale experimental setup is designed to study the hydrodynamic parameters and the mass-transfer efficiency in a countercurrent flow of mixtures of Freon R21 and Freon R114 on structured packings in a column 0.9 m in diameter. The study deals with the local and integral parameters of separation of the mixture, the degrees of nonuniformity of the flow rates and concentration distributions of the liquid and vapor phases over a cross section and on the column wall, and the pressure difference while varying the number of packing layers and their rotation angle. The mass-transfer processes while independently varying the liquid and vapor flow rates over wide ranges are also investigated. Experimental data are presented to illustrate the effect of the operating parameters on the height of an equivalent theoretical plate, the relative pressure difference, and the distributions of the local parameters of the flows.     

Fluorination of pressure-polymerized C60 phases

The reactivity of O-, T- and R-phases of the high pressure-high temperature (HPHT) polymerized C₆₀ towards gaseous fluorine in the temperature range of 50-250 °C was investigated. The reaction products were characterized by FTIR, powder X-ray diffraction, SEM, EDX, and VTP-EIMS to determine the bulk stoichiometries, bonding patterns, phase compositions, crystalline structures and thermal decomposition behavior of the fluorinated polymers. At 1 h isothermal treatment duration, fluorinated products with various bulk stoichiometries were obtained from different polymer phases with the R-phase showing the highest fluorine uptake. At 250 °C, all C₆₀ polymers showed partial decomposition to unfluorinated C₆₀ monomer under fluorine atmosphere. At 200 °C, the fluorination of R-phase yielded a pure fluoropolymer most likely having a {C₆₀F_x}_n (x = 36-44) composition. The same fluoropolymer was presumably obtained from O- and T-phases in lower yields. The linear chain structure was suggested for this new fluorocarbon polymer in agreement with the molecular mechanics modeling calculations.     

Low-temperature phase formation in the SrF2–LaF3 system

Phase formation in the SrF₂–LaF₃ system was studied at temperatures ranging from 300°C to 450°C using nitrate flux. The solubility of LaF₃ in SrF₂ decreases with decreasing temperature. The equilibrium width of the solid solution region Sr_1−xLa_xF_2+x at 400°C, it is 44.6 ± 0.4 mol% LaF₃ (x = 0.446), at 350°C — 38.3 ± 0.7 mol% LaF₃ (x = 0.383), and decreases almost to zero at 300°C.     

Aeroelastic stability of heated functionally graded cylindrical shells containing fluid

The article is concerned with the analysis of panel flutter of heated circular clamped cylindrical shells made of functionally graded (FG) material, which are subject to a simultaneous action of the external supersonic gas flow and the internal flow of ideal compressible fluid. The effective properties of the material change throughout the thickness of the shell according to a power law and depend on temperature. The aerodynamic pressure is calculated based on the quasi-static aerodynamic theory. The behavior of the fluid is described in the framework of the potential theory. A mathematical formulation of the dynamic problem for elastic structure is developed based on the classical theory of shells and the principle of virtual displacements. Based on the results of numerical simulation the influence of different consistencies of the examined FG materials, thermal load, and internal flow velocity on the boundary of aeroelastic stability is analyzed.     

A note: Common due date assignment for a single machine scheduling with the rate-modifying activity

In this paper we study the single machine common due date assignment and scheduling problem with the possibility to perform a rate-modifying activity (RMA) for changing the processing times of the jobs following this activity. The objective is to minimize the total weighted sum of earliness, tardiness and due date costs. Placing the RMA to some position in the schedule can decrease the objective function value. Several properties of the problem are considered which in some cases can reduce the complexity of the solution algorithm.